Air pickup system



A ril 10, 1945.

- s; c. PLUMMER AIR PICK-UP SYSTEM 4 Sheets-Sheet 1 Filed Dec. 22 1941 INVENTOR Sfuarf C. P/ummer A 3, u .lri E- H 6 a m ATTORNEY Ap 1945' s. c. PLUMMER 2,373,414

- AIR PICK-UP SYSTEM Filed Dec. 22, 1941 4 Sheets-Sheet 2 April 10, 1945. 4

S. C. PLUMMER AIR PICK-UP SYSTEM Filed Dec. 22, 1941 4 Sheets-Sheet s INVEOR Swuarf C. P/ummer .ATTORNEY April 1945v 5. c. PLUMMER 2,373,414

AIR PICK-UP SYSTEM Filed Dec. 22, 1941 ATTORNEY 4 Sheets-Sheet 4 invention there is provided a ground station hav inary shock absorbing means in conjunction with at... g... 10, 1945. 2,373,414

AIR PICKUP SYSTEM Stuart Crosby Plummet, Wilmington, Del., assignor to All American Aviation, 1110., Wilmington, Del., a corporation of Delaware Application December 22,1941, Serial No. 423,999

24 Claims. (01. 258-12) UNITED STATES PATENT OFFICE? This invention relates to aviation and'more parsirable characteristics may be constructed from ticularly to devices for picking up burdens fro synthetic condensation polyamide fibers known the ground by aircraft while in flight. I commercially as nylon.

According to a preferred embodiment of the Aline of this type may be used'as the preliming two poles spaced apart with a ground loop a winch or reel which is free to rotate at the connected to the tops of the poles by releasable time that engagement ismad with the line atcouplings. The ground loop forms a horizontal tached to the burden to be picked-up. The elas-- upper ply, and a lower ply which i connected ticity of 'the line will accelerate the which or' to the burden which may rest upon-the ground. m reel thereby permittingrelatively heavy weights The aircraft, which may be an airplane, has an to be picked up. By virtue of a controlled brakarm depending from its underside which suping action on the winch or reel, the acceleration ports a hook or grapple in such position as to placed on the burden to be picked-up, .and in engage the upper ply of the ground loop as the turn the load imposed. on the pick-up line, winch, plane is flownov'er'the poles and between a verand aircraft, may be adjusted. This controlled tical projection of the poles. A pick-up line is braking action is only necessary where relatively connected to. the hook and to suitable take-up heavy loads are to be picked-up. With smaller devices within theplane. loads the pick-,up line, or the pick-up line in The present device is designed primarily for use combination with a ground loop, will provide sufon aircraft .that are traveling at high speeds. flcient energy absorbing action to permit pick Some means must be provided for absorbing the ups at relatively high speeds. initial shock set up when the pick-up hook en- For controlling the reel, according to the ingages the line supporting the burden to be-pickedvention a small electric motormay be used, cone up, 4 trolled by amanually operated switch operating Means have formerly been used in an attempt to the reel to pay out line or to reel inthe line slowly secure this'end, but they have necessitated the -or rapidly. The reel mayhave. anv accelerationaddition of weight, and mechanism which can control brake'element secured'thereto'which may t out of order, all of which is undesirable in app y a light load to the reel when the engagean aircraft. Previous devices have suggested the ment with theload starts to unwind the reel and use of shock cord such as that used for landthen, after a predetermined number of revoluing gears, and various other purposes on air tions of the reel, apply full braking pressure to craft. Shock cord is objectionable for the reason the reel. The full braking pressure may be so that, if it is made strong enough, and with a .adiusted as to permit the reel to turn where sumcient degree of elasticity to take up the shock the load imposed on the line would otherwise of impact, the opposite and equal reaction will break it or damage the aircraft. tend to throw the burden ahead of the line by 1 The small electric'motor may drive a coop rwhich it was picked-up, and in some cases even ating brake element of the acceleration-control to throw the burden over the top of the aircraft. brake to rotate the reel through a magnetic The dangers inherent in such a'condition are -clutch,,which-is operated automatically to conobvious. Attempts have been made to use other nect the motor to the brake'when electricity is materials which would stretch, and have a high applied to the motor. I The magnetic clutch has degree of tensile elasticity, but these materials a second position which holds the second control have proven unsatisfactory for the reason that broke element stationary when current is retheir elasticity has been such that it caused the a moved from the'motor. aforeindicated results, or soon became exhausted The pick-up arm may comprise a laminated so that it no longer performed the desired funcpole and may be pivoted toth u de of th tion of absorbing the shock at all. aircraft near the center of gravity of the craft. It has been found, according to the invention, This arm may have a guidewayon the back on that it is desirable for a shock absorbing member which slides a carrier or cleat supporting a hook to have the characteristics of high tensile .which extends from the back of the arm around strength, excellent elasticity. great elongation the side to project out 'in front of the arm. The

within its elastic limit, and long elastic memhook is provided with staggered barbsfor preory, i. e., slow returnto original length after plac- V n ing accidental disengagement 01' the ground ing under tension. It has been found, accord- D, I ing to the invention that a line having those'de- 5 The invention also consists in certain new and v Fig. 1.

derside of the fuselage.

original features of construction and combinations of parts hereinafter set forth and claimed.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereabout to pick up a load from the ground station, I

according to the invention.

Fig. 2 is a longitudinal detail section through the end of the pick-up arm. Fig. 3 is a cross-section on the line 3-3 of Fig. 4 is a transverse section through the axis of the acceleration-control reel.

Fig. 5 is a section on the line 5--5 of Fig. 4. Fig. 6 is a detail showing the manner of connecting the pick-up line to the reel.

Fig. '7 is a side elevation of the control reel. Fig. 8 is a detail of the pick-up hook. v Fig. 9 is a detail plan view of the pivot connection between the pick-up arm and airplane frame. Fig. 10 is a sectionon the line Ill-48 of Fig. 9

1 illustrating a bearing construction; and

explanation, but it will be understood that the details may be modified in variou respects without departure from the broad aspect of the invention.

Referring now to the drawings. and moreparticularly to Figs. 1 to 3 and 9-11, the aircraft is illustrated as a modern airplane indicated by I provided with a hatch 9 in the fioor of the fuselage. Pivotally mounted at the forward side of the hatch and near the center of gravity of the plane is a yoke It! for the pick-up arm 5. The yoke Ill has a Y-configuration and suitable pivot devices 6 may be provided for pivoting the Y branches to suitable structural members within the fuselage.

Lever I may be connected to yoke I to manipulate it. Suitable stops or catches, indicated by 8 and 8', engagewith the lever I to lock the pick-up arm .5 in desired position. The

catches 8 serve to lock the pick-up arm in ap proximatelythe position shown in Fig. 1, which is the approximate pick-up position for engaging the load. The catches 8 are for the purpose of locking the arm in position up against the un- The yoke Ill and hatch 9 are located at the-side of the fuselage and the pick-up arm is Placed at a slight angle to the axis of pivot I to permit the arm to'lie within the confines of the horisired the fuselage may beprovided with a longiand partially house the pick-up arm 5 in retracted position.

The yoke I0 is of Y or triangular configuration, comprising an axle member I! and two diagonal members l3 suitably welded thereto. The axle member extends across the hatch 9 and rests on suitable seats on the structural members It secured to the fuselage, the seats having removable straps 22 and forming bearings for the pickup arm (Fig.

The pick-up arm 5 is clamped to the yoke member ill by suitable clamps 23, each clamp comprising a seat secured to the yoke member and a removable strap for clamping the arm in its seat (Fig. 11). If desired, suitable cushions such as leather sleeves 24 may be interposed between the wooden pick-up arm 5 and the clamps 23 to preventdamage to the wood by the clamps.

up against the bottom of the fuselage. If detudinal recess indicated by H in 1 to receive 76 The winch 6|, on which a suitable amount of pick-up line 2 is wound, is preferably mounted forward of the hatch 9. This line is preferably unwound from the afterside of the winch 5! to facilitate removing the burden from the pick-up ri g when the winch is wound up to bring the burden into the plane as will hereinafter more clearly appear.

The pick-up arm 5 comprises a shaft which may be of the order of 15 feet in length. This shaft is made of comparatively light strong material and may be formed of a. comparatively heavy forward section 15, which may be of oak or other suitable sturdy material, and a laminated after-section [6 which may be of somewhat lighter material, such as spruce wood. The shaft may be tapered, gradually decreasing in size from its upper to its lower end.

Secured to the afterside of the after-section of the pick-up arm 5 is a track I! which may comprise a metal strip suitably shaped to space its edges from the body of the pick-up arm and suitably secured to the pick-up arm as by screws 4!. Slidably mounted on the track I! is a cleat or slider l8 having suitable flanges l9 extending around the edges of the track I! to insure easy permanent sliding action. The upper end of track i1 is free of abutments and bends away from the pick-up arm as at 42 and is secured to yoke I0 by a strut 43. Portion 42 permits the operator to put the cleat onto the track in the beginning of the picking-up operation, as is explained hereinafter. The lower end of the track H is provided with spring detents 20 and 2|. The first detent 20 permits the cleat to pass readily over it due to action of gravity and of the air stream but to restrict its return. The action of the lower detent 2| holds the cleat in operative position until it is forcibly removed from the track by the picking-up operation.

The provision of a heavy forward section and a lighter laminated after-section insures that the center of gravity of the cross-section of the pickup arm is forward of its center of area and this, together-with the laminated construction, prevents fiutter'and gives smooth operation.

- the rear of the. pick-up arm around the side to the front thereof and ending in a bill 25 provided with staggered barbs 26 and 21. The hook is also provided with an eye 28 to which the line 2 is attached. By extending the bill 25 of the hook forward of the pick-up arm the load may be picked up without introducing any turning or twisting action on the pick-up arm and thestaggered barbs 2i and 21 prevent accidental disenengagement as explained hereinafter. This type of hook also makes it possible to have the track I on the back ,of the pick-up arm where the-track will not be damaged by'contact with the pick-up loop nor will it be ,so free to accumulate ice or dirt.

The ground station may comprise two poles 00. set in the ground a suitable distance apart,

say 20 feet, and having a suitable height, say 20 feet, to the upper end of which may be connected flags 99. The corners of theflags 39 may be provided with releasable couplings 85 which engage ground loop 3| having an upper ply 32 suspended between the poles and a lower ply 39 connected to the burden 30 which may rest upon the ground.

Referring now to Figs. 4-7, the control device for paying out or drawing in the transfer line2 comprises generally the winch BI, an automatic brake 80 operativeto place the maximum desired braking effort upon the winch upon a predetermined number of revolutions thereof, an electric motor I60 for driving the winch andan electromagnetic clutch I80. cludes a frame 50 suitably secured to the frame of the airplane, and whichsupports the winch The transfer line 2 is attached at 'one end to the winch BI, preferably by a connection which will permit the end to be released in the event of emergency. Referring to Fig. 6, the end of the line 2 is secured in a socket 200 threaded on a stud 20I carried by or formed integral with a weakjournaled at one end in a bearing 63 mounted in the side wall 48 of the frame 50 and-provided with a seal 65 and a cover 66. The winch 9| includes a cylindrical rim 61 connected by a web 88 to a hub 69 and has at one end a retaining flange II. A second retaining flange I2 is'attached to the rim 61 as by bolts 13. The reel 0| The control device in in a similar direction to 00 causing the rollers 91 a ring m. Thus thebearing a1 constitutes with i the bearing 09 the main bearings for supporting v the shaft 62 rotatably in the frame 50.

Cooperating with the brake disc 9| is a complementary brakedisc or shoe 92 of annular form having frictional lining '90 on its face bearing against the brake plate 15. The brake disc 92 is resilientlyv urgedlightly toward the brake plate II by bolts 2I0 extending through the brake disc 92, the interior opening of the ring I6 and through a suitable opening in the brake disc 8|.

Bolts 2) carry springs 2| 2 bearing against the brakedisc 8| and against an adjusting nut or nuts 2I3.'

Extending from the brake disc 92 is a plurality (in the present case 3)' of studs 94 whichextend through openings in the brake disc 8 I. Plvotally connected to each stud 94 by a pivot pin 95 is an operating lever 99 which carries at the end of its shorter arm a roller 91 adapted to bear against a I box 90 projecting from the adjacent face of they brake disc 8 I. The long arm end of the actuating lever 98 is pivotally connected as by a pivot pin I00 to a socket IOI attached to an actuating rod I02 which extends through the journal and bear-, ing portion 89. The actuating rod I02 is connected by a. spring I03 to a stud Ifll which is threaded intoa disc I05.

Upon movement of the disc I05.(eflected in a manner hereinafter to be described) in.a direction away from the brake disc 9! (to the right asviewed in Fig. 4) the actuating rods I 02 are moved thereby rock the levers to bear upon their respective bosses 99 and to clamp the brake disc 92 and the brake disc 0i against the brake plate I5. Owing to the lug and notch connection between the brake plate 15 and the reel 8|, the brake is I thereby permitted to shift axially and allow the is suitably secured against axialor angular dis- 1 placement on the shaft 62 and abuts a positioning shoulder I4. Annular extensions I0 are secured.

to flanges ll and 12 to provide for desired num- I9 which are set in notches I'I formed in lugs 19 which extend inwardly from the cylindrical, porclamping action to take place. I In order to cause the actuating disc I05 to move outwardly and to apply the brake 80 upon a predetermined number of revolutions of the winch 9|, an automatic brake actuating mecha nism is provided which will now be described.

I he disc I05 is non-rotatably connected to the Journal and bearing member 90 by a stud 0 which extends through the disc I05 and is threaded into the member 99. The disc I0! is mounted on a collar III having a flange 2 at one end and a ring I I 2 at the other end, the disc I05 and collar III being thus permitted to have relative axial sliding movement which is limited in extent by-the flange H2 and ring 9.

The .collar III is adjustably threaded onto an outer sleeve Ill and is positioned non-rotatably thereon by a spring I I5 adapted to enter'into any tion 91. The plate I9 thus is capable of moving I axiallybut is locked against angular movement relative to the winch BI.

The brake 00 cooperates with the brake plate "II and includes a driving brake disc or frame 9| having a suitable friction lining 02 secured to its face and adapted to bear against the brake plate IS. The brake disc M is carried by (and in the present embodiment is integral with) a hub 00 which carries a bearing 8| mounted on the shaft 92 and retained by a ring 90.

The hub 03 has ajoumal and bearing portion 90' which receives a bearing 90' positioned by a one of a plurality ofcircumferentially spaced,

axially extending notches or slots 0. The

- the axial position of the collar III and: thereby spring I I5 can be raised out of its notch and, the collar I I I turned in the outer sleeve Ill to adjust adjust the time at which the flange II2 strikes against the disc I".-

ring 9|. Asleev 99 abutting a shoulder 90 on the shaft assists in positioning the bearing 90 on the shaft 92. The bearing and journal portion 99 is itself joumaled in a bearing "mounted in the side wall 40 of thei'rame "and secured by The outer sleeve III is threaded onto an inner sleeve II! by large screw threadswhich permit the sleeve Ill tOItlll'Il on the inner sleeve Ill and to be advanced thereby in an axial direction.

. The inner sleeve II! is non-rotatably secured to the shaft 62 asbya key I I 9.

Movement of the sleeve I It on the inner sleeve H1 is limited by a flange H9 at theinner'end of the inner sleeve Ill and by a ring I20 non-rotatably secured on the shaft 82 as by a'key I2I and ajnut I29-and abutting the outer end of the sleeve III. In order to permit axial movement of the outer sleeve III on the inner sleeve II I, a recess I24 is formed in the outer sleeve IN of sufiicient diameter to accommodate the ring I20. For the purpose ofm'anually turning the outer sleeve H6 (for resetting purposes hereinafter described a flange I22 provided at its outer end having sockets I25'for aspanner.

H4 and preferably seats in a circumferential groov I34 to prevent displacement of the ring I30, 9. suitable brake lining I33 being provided. The brake ring I30 is formed with a lug or extension |3| having an opening through which the stud loosely passes whereby the brake ring is non-rotatably connected to the member 86.

For a more complete description of the winch and automatic control therefor attention is called to my application Serial No. 333,081 filed May 3, 1940, entitled Transfer apparatus.

It will nowbe seen upon rotation of the shaft 62 whichcarries the winch 6|, the inner sleeve III is rotated correspondingly and through the action of its threads causes the outer sleeve IIB to be moved axially in a direction away from the frame member 49 (to the right, as viewed in Fig.4). 'As the outer sleeve H6 moves outwardly, the flange H2 is brought into abutment with the disc I and moves it in a corresponding direction, thereby exerting a pull on the several actuating rods I02 and causing the brake disc 92 and the brake disc 8| to clamp more tightly against the brake ring I5. The brake 80 there- 'fore is automatically applied with continuously increasing force until the winch 6| is halted or until the end of the socket or recess I 24 abuts the ring I20.

In order to rotate the winch 6| so as to draw in or pay out the transfer line 2, suitable rotating means are provided, which in the present case, comprise a driving motor I60 connected to the brake 80. A drive gear I50 is rigidly secured to the brake disc 8| as by bolts I5l and a driving pinion I52 meshes with the gear I50. The driving pinion is carried on a shaft I53 of reduction gearing denoted in general by I54 and secured to the frame member 50..

Thereduction gear I54 comprises a worm wheel II0 set in a groove I59 in slidable shaft I63, which ,eflectively locks shaft I63.

When electric power is applied to motor I60, the electro-magnetic disc I65 is automatically energized which exerts a magnetic pull on disc I62, axially sliding it together with shaft I63 and gear I58, freeing disc I62 from brake element |6| and engaging it wlth'element I65 to exert driving power upon shaft I63 to drive the winch 6| in either direction.

Due to the high reduction of gear reducer I56 a small braking effort is sufl'lcient to hold the gear I50 and brake 80 stationary. The electro-magnetic brake I6I, I62 also acts to bring winch gear I50 quickly to rest when electric current is removed from motor I60. In some cases, when a sufliciently low pitch worm is used in the reduction gear I54, the brake 16L, I62 may be dispensed with entirely.

A five position push button control indicated in general by I61 on the top of frame 50 is protion as to pay out line 2 slowly or rapidly. The

I on shaft I53, wheel id'being driven by worm I56 which is connected to gear I51 and suitably .journaled in the gear box; Gear I51 is driven by pinion I58 mounted on axially slidableshaft I63.

The reduction gear may be of high speed ratio,

shaft'-|63.' The motor shaft I64 may have an electro-magnetic disc I65, which is magnetized by solenoid winding I6la when 1 electric power is applied to the 'motor I60.

' He' may also adjust sleeve IM to When no electricity is applied to winding I6Ia, f

the disc I62 is held against the brake surface on disc IN by a spring disc I68 acting between a plate I66 fixed to the casing and a slidable plate fourth and fifth positions are for slow and rapid "forward respectively for causing the motor to power drive the winch 6| to reel in line 2 slowly or rapidly, depending upon the weight of the burden as compared to the power of the motor.

It will be understood that the push button control I6! is connected to a suitable source of electric power (not shown) and to the electric motor I60 and to the clutch I66 through suitable wiring and motor speed regulating devices (not shown).

Operation and comments To use the pick-up system, the ground loop 3| is engaged with the releasable couplings 35 on the tops of the poles 30 and the burden 34 is connected to the ground loop, the burden resting on the ground. The plane is' preferably provided with a pick-up operator in addition to the pilot.

The pick-up operator, befor approaching the ground station, gets his pick-up apparatus in readiness for the pick-up operation. He lowers his pick-up arm slightly from its inoperative position up against the fuselage, he puts the oleat I8 on the upper end of the track I1. and operates the electric control I61 to drive motor I60 to pay out enough line 2 to allow gravity assisted by the air stream to pull the cleat down to the position shown in Fig. 1 between detents 20 and 2|,

He also may adjust nuts 2I2 to give the desired frictional resistance between brake elements 92, I5, and III." This sets the resistance applied to the winch 6| for the initial relatively free revolutions it will make after the load is engaged.

reset the'brake (sleeve I I4 having been brought I 20 by a previous pick-up operation) and to control the maximum braking. effort it is desired to impart to the winch for the picking up operation. He also may adjust the'collar III toset thenumber of relatively free turns, the winch will make after engagement by the load before applying tension to springs I03 to app y the -It will be understood that when the winch 6| is positively driven by the electric motor I60 in against shoulder either direction, no relative movement takes place between the main brake elements 02, II and 8| and consequently no variation in braking friction is caused. It is only when the electric motor is stationary and the driving brake element 8| is held stationary that rotation ofthe winch causes any change in braking function on main brake 80. This condition occurs when the reel is forcibly unwound by pick-up line 2 due to engagement of the pick-up hook 3 with the ground loop Continuing with the pick-up operation, the

pick-up operatorthen lowers the pick-up arm to a position approximating that of Flgfl and the pilot of the plane brings the plane over'the ground station with the arm directed between the poles 30 in such manner as to engage the pick-up arm withv the upper ply of the ground loop above the hook. The ground loop then slides along the smooth front face of the pick-up arm until it engages the hook, the force of contact pulling the hook free of the pick-up arm and the load is sulliciently light,- he reels it in last until the burden approaches the plane after which he operates take-up switch I01 to maneuver the burden close to the reel within the plane. The control switch I81 is then placed in neutral I position. stopping the reel and holding the burden causing the pick-up line automatically to pay the hook with the ground loop and the four revolutions of the drum act to pay out about 12 more feet. If the load is heavy enough, the drum will continue to pay out with the brake fully applied. With light loads there may be no further'paying out after the brake is fully applied.

The action of the winch and the of the nylon pick-up line and nylon ground loop on the burden iness for Y terial which has similar stationary, after which the burden is manually lifted inside the plane. The-reel may be operatedv to-unwind the ground loop so it may be detached from hook 3 and to put the reel in readthe next picking-up operation.

Thus, a pick-up system has been described which is eflicient and reliable in operation. The

use of a light weight, stretchable, slow recovery pick-up line permits'the picking up of anyloadthe plane can handle without shock and eliminates all spring and slider devices. When used with the pay-out drum, the elongation of the nylon acts to reduce stress on the line during the period-in which speed. Byvarying the braking eflort on the drum the acceleration of the load can be nicely controlled. 1

Although nylon has been given for purposes of illustration, as constituting the best material known to me at the present time, for the pick-up line 2 and ground loop line- 3|, it will be understood that the invention is applicable to any mashock-absorbing properties. Such a material must have a substantial elongation under stress, for example in the range 1. of from to elongation, it must alsohave the property of slowly returning the energy stored is as follows. At the moment of impact of the hook with'the ground loop, the plane may be traveling 120 miles per hour, and it is desiredto accelerate the burden from zero velocity to the velocity of the plane with as little shock on the plane, burden and equipment as possible. This can be done by making the acceleration of the burden as slow as possible. The elongation of the nylon rope and the paying out of the drum cooperate to this end.

Upon the first force being applied to the pickup line 2 due to contact of hook 8 with ground loop M, which may be considerable even with light loads and with light equipment, due to the high speeds of aircraft travel, the nvlon exerts' an accelerating force on the winch. The great elongation of thenylon gives time to overcome the inertia of the winch and to start it rotating. After the winch is accelerated, the brake is gradually applied to the winch to prevent too rapid paying out of the line 2 and to continue apply- .ing an accelerating force to the burden. The

continuing of the paying out even after the brake is fully applied limits the force applied to the line 2 and permits the picking up of loads heavier than would otherwise be. possible.

After the nylon is fully elongated, it tends to return to its original length but its elastic memof the plane, the pick-up operator then operates or slow, dependingupon' how heavy the load. If

up in the line by the stress causing the elongation,

i. e., long elastic memory. Slingshot action, i. e.,

overshooting of the burden with attendant slackness on the pick-up line is thus avoided. However, the material must have the property of returning to its original length within a short time.

The elongation must not be permanent. Nylon fibers, from which the pick-up rope and ground loop are made, are a well-known product manufactured and sold by E. I. du Pont de' Ne nours & Co. Nylonis known as a synthetic linear condensation polyamide, capable of being drawn into pliable strong fibers showing by characteristic X-ray patterns orientation along the fiber axis. This material is disclosed in Carothers Patents Nos. 2,071,250; 2,071,251; 2,130,523 and 2,157,116.

Nylon fibers have high tensile elasticity, high bending elasticity and a relatively long elastic memory. The nylon fibers are formed into yarns and the yarns maybe braided to form the nylon line. The braiding operation bends the fibers, putting them into wavy configuration. When stress is applied to the line, the nylon yarns will change both their wavy configuration and length. By tensile elasticity is meant. the ability of a length, or substantially its original length, when released from tension. This tensile elasticity-is expressed in' terms of elongation without destruction, and the percent 01 recovery within a given time. Bending elasticity as herein used means the ability of a fiberi after it has been braided the take-ups'witch I81 to reel in theline fast into a pattern which gives it a wavy shape, to return to its original shape. For example, assume a fiber is given a form such as that usually shown to describe a wave movement; if, after being placed under tension, this fiber not only resumes its length, but also its original wavy shape, it would have, as the terms are herein used, both tensile elasticity and bending elasticity. Its elastic memory is then measured in terms of the time the drum is getting up to that it requires for the individual fiber to resume its original or substantially its original condition before that tension was applied to it.

Nylon fibers, when first formed from solution or melt, have thepeculiar characteristic of being capable of being stretched to many times their original length without exhibiting any substantial tendency to return when tension is released. When subjected to. sumciem; cold drawing, 'however, the fibers acquire an .excellent elasticity, that is, tendency to return to original condition aircraft, and means for engaging said burden or from said aircraft while in flight including a sufafter stretching. For this reason before braiding the fibers into a line it is necessary that they sufficiently cold drawn to the point where they exhibit such excellent elasticity.

Another advantage of the use of a line of this type is that it is moisture repellent, and, therefore, may be used where there is rain without the moisture ailecting the qualities of the line. Further, such a line will not tend to accumulate ice internally when passing through icing conditions. Other materials which tend to absorb water will hold the water within the fibers of the line, and due to the movement through the air, this water and the entire line may be cooled to a point where the water will freeze, thereby restricting the action of the fibers, and preventing their proper function. In addition. a line comprised of the material'herein proposed is notaffected markedly by chan es in temperature. A further advantage of the line is that, where used for a pick-up loop, it may be dropped on the ground without regard to ground conditions whereas ordinary line would tend to accumulate mud and dirt.

The placing of the pick-up pole or arm near the center of gravity of the plane puts the equipment and locates the pick-up operator at the most advantageous position with respect to the operation of the plane. The location of the arm forward also allows room toswing the arm u a ainst the fuselage when it is folded out of use. The use of the laminated ole greatly increases the strength of the arm and helps eliminate flutter. The placin of the center of ravity of the pole forward of the center of area also eliminates flutter.

The placing of the guideway on the back of the arm leaves the front leading edge smooth for mo e efllcient en agement of the ground loo It also prevents dirt ettin into the guidewav when the ship is on the ground and reduces the op ortunit for ice to form. The extendine'oflthe hook around to the front of the arm is accomplished without affectin the line of action of the hook or cansn: twisting stress on the a m. The st g ere barbs on the end of the hook revent accidental disenga ement of the ick-u l op. The locat n of the pick-u line on the after side of h w nch ermits winding of the line to in the burden further into the plane. facilitating handlin of the burden b the pick-up operator.

Wh le certain novel features ofthe invention have been disclosed herein. a d are pointed out in the annexed claims. it will be understood that various omissions. substitutions and chan es ma be made by those skilled in the art without departing from the spirit of the invention.

What is c aimed is:

1. In a pi k-up s stem. a line havin the characteri'stic of hi h tensile stren t ex ellent a synthetic plastic material having the inherent characteristic of high tensile strength, excellent elasticity, relatively great elongation and long elastic memory, a'burden adjacent the earth, an

ficient length of said line to prevent, substantial rebound of said burden.

3. In an air pick-up device, a ground station comprising spaced poles, releasable connections secured to said poles, a ground loop line secured to said releasable connections, said ground loop line having an upper ply extending between the tops of the poles and a lower ply, a burden secured to said lower ply, an aircraft, a pick-up line depending from said aircraft, a grappling device on the end of said pick-up line adapted to engage said upper ply, at least one of said lines comprised of a material having suflicient stretch, upon the upper strand being engaged by said grappling device, to permit gradual acceleration of aid load and having sufiicient energy absorption and sufficiently slow return to prevent rebound of said burden.

4. In a pick-up system, an aircraft, a burden to be picked-up by said aircraft while in flight, a winch'comprising a frame, a drum journaled in said frame and having a first braking element se cured thereto, a driving member also joumaled in said frame and having a second braking element cooperating with said first braking element, a reduction gear driving said driving member, a high speed electric drive motor, an electro-magnetic clutch interposed between said electric drive motor and said reduction gear, said clutch acting to drive said reduction gear when electric power is applied to said motor and holding said reducv tion gear stationary when electric power is remember stationary when no electric power is aplied to said motor;

6. In a system for launching an object to be pulled through the air,-a towing craft, an object to be towed, a line for connecting said craft and I said object, said craft and object having widely different speeds of movement thereby impressing sudden pull on said line, said line having the characteristics of high tensile strength, excellent elasticity, relatively great percentage elongation. and long elastic memory, whereby said line absorbs the shock, due to the sudden pull imposed thereon, without substantial rebound of said object.

7. Apparatus according to claim 6 in which at least a part of said line is composed of nylon fibers.

. 8. In a system for launching an object to be pulled through the air, a towing aircraft, an object to be towed by said aircraft, a line for connecting said craft and said object, said craft and object having widely different speeds of movement at the time said line becomes taut, said line being made from a material whose fibres have the characterisaircraft and said object including a line, a winch on which a length of said line is wound, means for applying a retarding force to said winch, said line having the characteristics of high tensile strength and relatively great percentage elongation and long elastic memory so as to minimize the shock necessary to overcome the inertia of said 'winch, the retarding force of said winch there-' after acting to apply accelerating force to said a object as said winch unwinds.

11. In an air launching system, an aircraft, an object to be accelerated by said aircraft, apparams for establishing connection between said aircraft and said object including a line, a winch on which a length of said line is wound, means for applying a retarding force to said winch, said line having the characteristics of high tensile strength, excellent elasticity, relatively great percentage elongation, and long elastic memory, aid line absorbing the shock necessary to overcome the' inertia of said winch without substantial rebound, the retarding force of said winch thereafter acting to apply accelerating force to said object as said winch-unwinds.

12. man air pick-up system, an aircraft, an'

object to be picked up by said aircraft while the latter i in flight, apparatus for establishing connection between said aircraft and said object including a line, a winch mounted on said aircraft,

. means for applying a retarding force to said winch, saidline having a length wound on said winch and a length connected to said object, at least a part of said line being made from a material whose threads have the permanent characteristics of high tensile strength, excellent elasticity, at least ten .per cent elongation, and long elastic memory, said line absorbing the shock necessary to overcome the inertia of said winch without substantial rebound, the retarding force of said winch thereafter acting to apply accelerating force to'said object as said winch unwinds.

- 13. In an air pick-up system, an aircraft, an

. bject to be picked up by saidaircraft while the latter is in flight, apparatus for establishing connection between said aircraft and said object including a line, said lin comprising a length'in the form of a loop connected to said object, a winch on said aircraft comprising a framework secured to the aircraft, a brake support rotatably mounted on said framework, a drum also rotatably mounted on said framework, a main brake acting between said support and said drum, an

electric motor, gearing between said electricmotor and said brake support, a motor brake for holding said brake support stationary, a unitary, rigid, smooth pick-up arm, means pivoting said pick-up arm to said aircraft near said winch, a track extending the length of said pick-up arm on the rear side thereof, a cleat slidable on said track and carrying a hook, said arm carrying yieldable means for permitting said hook to disengage itself from said arm upon contact'with said loop, said track having a portion at its upper end accessible for placing said cleat on the track, said line including a length wound on said drum and secured to said cleat whereby said smooth unitary arm may engage said loop and guide the same into said hook, the hook thereupon disengaging itself from said arm, the pull of said object unwinding the length of said line from said drum, said line having the characteristic of high tensile strength, relatively great percentage elongation with long elastic memory. 1

14. In a system for, pulling an object through the'air, a pulling craft,'a towed air-borne object, a line connecting said craft and said object, said line having the characteristics of high tensile strength, high elasticity, 10 to 30 per cent elongation, and long elastic memory, whereby said'line absorbs shock due to sudden pull imposed thereon without substantial rebound of said object.

15. Apparatus according to claim 14 in which at least a part of the line is composed of nylon and said drum, means for holding said brake support stationary, a unitary, rigid, smooth pick-up arm, means pivoting said pick-up arm to said aircraft, a hook detachably supported by said arm, said line including a length Wound on said drum and secured to said hook whereby said smooth unitary arm may engage said loop and guide the same into said hook, the hook thereupon disengaging itself from said arm, the pull of .said object unwinding the length of said line from said drum against said brake, at least "one of said lengths of line having the characteristics of high tensile strength, excellent elasticity, 10 to 30 per cent elongation, and long elastic memory, whereby energy to said line is dissipated.

17. Apparatus according to claim 16 in which at least a part, of the line is composed of nylon.

18. In a shock absorbing system,;first and second elements having different motions, connecting apparatus comprising a winch mounted on one of said elements and a line connecting said winch and saidother element, said winch comprising a elasticity, relatively great elongation, and long V elastic memory, the pullof said line on said drum unwinding said drum, the elongation of said line minimizing the shock necessary to overcome the inertia of said drum without substantial rebound while said drum is accelerating and the braking effort is being graduallyapplied thereto, the full retarding force of said brake thereafter acting to applyaccelerating force to said line.

19. Apparatus according to claim 18 in which at least a part of the line is composedof nylon. 20. In an air pick-up system, an aircraft, an

secured to the aircraft, a brake support rotatably mounted on said framework, a drum also rotatably mounted on said framework, a main brake acting between said support and said drum, means for holding said brake support stationary. said line also comprising a second length wound on,

said drum, means controlled by pull on said second length of line for gradually applying said brake to said drum from a condition where said drum rotates relatively free of said brake to condition of full braking effort applied to said drum,

a hook secured to said second length of line and adapted to engage said loop for the pick-up, said line having the characteristics of high tensile strength, excellent elasticity, 10 to 30 per cent elongation, and long elastic memory, the pull of said line on said drum unwinding said drum, the elongation of'said line minimizing the shock necessary to overcome the inertia of said drum without ubstantial rebound while said drum is being accelerated from rest and the braking eifort is being gradually applied thereto, the full retarding force of said brake thereafter acting to apply accelerating force to said object as said drum further unwinds. Y

21. In a system for changing th velocity of an object, an object of substantial mass subject to motion, a body of substantialmass with respect to which said object has relative motion, a line for connecting said body and said object, said line aarasu strength, high elasticity, relatively great percentage elongation, and long elastic memory, whereby said line absorbs shook due to sudden pull imposed thereon by the inertia of said object without cans-- ing substantial rebound of said object.

22. In a shock absorbing system, first and second elements having diiierent motions, connecting apparatus comprising a winch mounted on a one of said elements and a line connecting said being subject to pull to resist said relative motion,

, said line having the characteristics of high tensile winch and the other element, said winch including a drum, means for applying a retarding force to said drum, said line having a length wound on said drum, said line including a length having the characteristics of high tensile strength, excellent elasticity, relatively great percentage elongation and long elastic memory, the pull of said line unwinding said drum, elongation of said line minimizing the shock necessary to overcome the inertia of said drum without substantial rebound while said drum is accelerating, th retarding force of said winch thereafter acting to continue to apply force to said line.

23. In a system for launching an object to be pulled through the air, a towing aircraft, an object to be towed by said aircraft, and a line for connecting said aircraft and said object; said air, craft and object having difierent speeds with respect to each other thereby impressing sudden pull on said line, said line having the characteristics of high tensile trength, at least ten per cent elastic elongation and long elastic memory whereby said line absorbs the shock due to the sudden pull imposed thereon without substantial rebound 'of said object. 24. Apparatus according to claim 23 in which at least a part of the line is composed of nylon fibers.

STUART CROSBY PLUMMERJ 

